RECOVERY PLAN Atlantic Salt Marsh Snake (Nerodia clarkii taeniata) U.S. Fish and Wildlife Service RECOVERY PLAN FOR THE ATLANTIC SALT MARSH SNAKE (Nerodia clarkii taeniata) Prepared by U.S. Department of the Interior Fish and Wildlife Service Southeast Region Atlanta, Georgia with assistance from Paul E. Moler Florida Game and Fresh Water Fish Commission Wildlife Research Laboratory Gainesville, Florida Approved: am, Jr. Regional Director, U S Fish and Wildlife Service Date: December 15, 1993 DISCLAIMER Recovery plans delineate reasonable actions which are believed to be required to recover and/or protect listed species. Plans are published by the U.S. Fish and Wildlife Service, sometimes prepared with the assistance of recovery teams, contractors, State agencies, and others. Objectives will be attained and any necessary funds made available subject to budgetary and other constraints affecting the parties involved, as well as the need to address other priorities. Recovery plans do not necessarily represent the views nor the official positions or approval of any individuals or agencies involved in the plan formulation, other than the U.S. Fish and Wildlife Service. They represent the official position of the U.S. Fish and Wildlife Service only after they have been signed by the Regional Director or Director as approved. Approved recovery plans are subject to modification as dictated by new findings, changes in species status, and the completion of recovery tasks. Literature Citations should read as follows: U.S. Fish and Wildlife Service. 1993. Atlantic Salt Marsh Snake Recovery Plan. Atlanta, Georgia. 19 pp. Additional copies may be purchased from: Fish and Wildlife Reference Service: 5430 Grosvenor Lane, Suite 110 Bethesda, Maryland 20814 301/429-6403 or 1-800-582-3421 Fees for recovery plans vary, depending on the number of pages. EXECUTIVE SUMMARY Current Status: The Atlantic salt marsh snake is listed as a threatened species and is restricted to the salt marshes of Volusia, Brevard, and possibly Indian River Counties, Florida. Habitat Requirements and Limiting Factors: The Atlantic salt marsh snake (Nerodia clarkii taeniata) inhabits brackish coastal marshes predominantly vegetated with glasswort (Salicornia spp.) and salt grass (Distichlis spicata). Black mangrove (Avicennia germinans) is typically present but not predominant. To the south, as mangroves become more prevalent, the Atlantic salt marsh snake is replaced by the conspecific mangrove water snake (N. clarkii compressicauda). Recovery Objective: Delist the Atlantic salt marsh snake when recovery criteria are met. Recovery Criteria: This snake may be considered for delisting if (1) there is no evidence of significant genetic introgression (genetic exchange limited to a very narrow hybrid zone) from the Florida banded water snake (Nerodia fasciata pictiventris) into adjacent populations of the Atlantic salt marsh snake (Nerodia clarkii taeniata), (2) adequate habitat protection is maintained, and (3) self-sustaining populations of 100-200 adult snakes at each of 10 secure, discrete sites are established throughout Volusia County. These numerical goals are subject to revision as more information becomes available on the biology of the Atlantic salt marsh snake. Actions Needed 1. Conduct basic ecological studies. 2. Determine and map distribution. 3. Identify habitat protection measures. 4. Conduct taxonomic assessment. 5. Determine relative abundance within occupied habitats. 6. Determine extent of genetic introgression. 7. Develop a contingency plan for catastrophic events. 8. Disseminate information about Atlantic salt marsh snakes. Costs ($000’s): Year Need 1 Need 2 Need 3 Need 4 Need 5 Need 6 Need 7 Need 8 Total FYi 25 15 8 5 4 57 FY2 25 15 5 3 48 FY3 10 7 2 19 FY4 2 10 6 18 FY5 10 _ 10 Total 50 40 8 19 20 7 2 6 152 Date of Recovery: Delisting should be initiated in 2000 if recovery criteria are met. : RECOVERY PLAN OUTLINE I. INTRODUCTION Description 1 Taxonomy 2 Distribution 3 Habitat 5 Life History/Ecology 5 Reasons for Listing 6 Conservation Measures . 7 II.RECOVERY A. Objective 9 B. Outline Narrative Recovery Actions Addressing Threats. 9 C. Literature Cited 13 III. Implementation Schedule . 15 IV. List of Reviewers 18 I. INTRODUCTION Description The Atlantic salt marsh snake (Nerodia clarkii taeniata) was listed as a threatened species on November 29, 1977 (U.S. Fish and Wildlife Service 1977). It was described by E. D. Cope in 1895 as a subspecies of the mangrove water snake, Natrix compressicauda (New World water snakes are now assigned to the genus Nerodia). It has a complex taxonomic history which is addressed in the next section. There are three subspecies of salt marsh snakes, the Gulf salt marsh snake (Nerodia clarkii clarkii), mangrove water snake (N. c. compressicauda), and Atlantic salt marsh snake (N. c. taeniata). Their dorsal patterns are formed from a basic pattern of four rows of dark blotches running from head to tail (two lateral and two dorsolateral rows) on a lighter background. In the striped forms, the blotches fuse linearly to form stripes; in the banded forms, the blotches fuse across the back to form bands. In partially striped individuals, it is invariably the anterior portion of the body that is striped, with the pattern posteriorly consisting of bands or rows of unfused blotches. The lateral stripes have a greater tendency than do the dorsolateral stripes to break down posteriorly into rows of blotches. The Gulf salt marsh snake (Nerodia clarkii clarkii) has a dorsal pattern that is completely striped, or nearly so, with dark brown to black stripes on a tan background. It is not unusual for the lateral stripes in this form to break down posteriorly into rows of blotches. The mangrove water snake (N. clarkii compressicauda) may be uniformly orange in color, but it more often has a pattern of dark bands on a lighter background. Individuals from throughout the range of the mangrove water snake may be partially striped; in these specimens the striping is typically limited to the neck region, but occasional specimens may be more extensively striped. Coloration in the mangrove water snake is extremely variable, with the background being gray, straw, or reddish and the bands being black, brown, or red. Populations of mangrove water snakes characteristically include at least some individuals that exhibit reddish or orange pigmentation. The Atlantic salt marsh snake (N. c. taeniata) is a partially striped salt marsh snake that reaches a maximum length of at least 82 cm (32 in.), although it is typically less than 65 cm (26 in.) in length. The pattern consists of a gray to pale olive background with black to dark brown stripes anteriorly, the stripes breaking up into rows of spots posteriorly. The extent of the striping is variable, but most individuals from the coastal marshes of Volusia County are striped on at least the anterior 30 percent of the body. The venter is black with a central row of large cream to yellowish spots. As in the case of the dorsal striping, this ventral pattern is best developed anteriorly and tends to break down posteriorly. The red pigmentation characteristic of mangrove water snakes is conspicuously lacking in Atlantic salt marsh snakes from the vicinity of Edgewater, Volusia County, and northward (i.e., the area from which the form was described). Hebrard (1979) reported coloration for’ 23 specimens from the southern Indian River Lagoon, near the Volusia-Brevard county line. Of these, 7 (30 percent) exhibited orange or reddish pigmentation either dorsally or ventrally. It is unclear at this time whether the reddish pigmentation reported by Hebrard should be interpreted as indicating intergradation with the mangrove water snake. The series of 25 specimens for which Hebrard provided pattern descriptions had dorsal stripes on 0 to 100 percent of the body; only 8 (32 percent) had dorsal stripes on more than 30 percent of the body, but 3 (12 percent) reportedly had dorsal stripes on 100 percent of the body. (In terms of pattern formation, the vertebral stripe is actually the lighter background color which is visible between the two dark, dorsolateral stripes.) There are several characters of morphology and color pattern that distinguish the salt marsh snakes from the related freshwater species of Nerodia, but one of the most reliable is the number of dorsal scale rows. The salt marsh snakes have the dorsal scales in 21 rows at midbody, whereas the freshwater banded water snake has the scales in 23 rows. Also, those populations of salt marsh snakes that are at least partially striped are easily distinguished from the freshwater form, which is completely banded. Taxonomy The Atlantic salt marsh snake has a complex taxonomic history, having been known under various combinations of generic, specific, and subspecific names. The North American water snakes were long included within the genus Natrix, but Rossman and Eberle (1977) restricted that genus to Eurasia and erected the genus Nerodia to include many of the North American species previously included within Natrix. At the species level, the salt marsh snakes have at various times been treated as a separate species or as subspecies of two related freshwater species. Both the Gulf salt marsh snake (Nerodia clarkii clarkii) and the mangrove water snake (N. clarkii compressicauda) were initially described as separate species. Based at least partly on reports of hybrids between N. c. clarkii and the freshwater broad-banded water snake (N. fasciata confluens), Clay (1938) reduced the salt marsh snakes to subspecies of N. sipedon, a name that at the time applied to all of the banded water snakes of eastern North America. Subsequently, Conant (1963) elevated the subspecies of N. fasciata to species status to include the three salt marsh snakes and the three southern freshwater subspecies: N. f fasciata, N. f confluens, and N. f. pictiventris. At the time that the Atlantic salt marsh snake was listed as threatened, it was regarded as a subspecies of the southern water snake, N.